This invention relates to a high pressure fuel injector that is suitable for high speed engines, particularly those having fuel injection controlled by an electronic fuel injection system. This invention relates to our fuel injector system described in U.S. Pat. No. 5,042,441, issued Aug. 27, 1991, entitled, "Low Emission Combustion System for Internal Combustion Engines". The fuel injector system of the referenced patent utilizes a high frequency pulsing in order to deliver a pulsed spray to the combustion chamber for fuel efficient combustion. The fuel injection system of the present invention can be adapted to accommodate the pulsed injector feature of our former patent.
In developing fuel injectors for high pressure, high speed engines, fuel economy and low emissions are important considerations. Accurate timing and metering of fuel is essential to achieve these goals. Prior art systems have inherent mechanical design limitations that render them unworkable for high pressure systems. In many such systems back pressures and reflected hydraulic pressure waves prevent the injector needle from firm seating and instantaneous cutoff once the fuel delivery cycle has been completed. This results in a lag in the fuel shut-off and leakage of additional fuel into the combustion chamber which is added in an inappropriate time during the engine cycle. This results in smoke from incomplete combustion and wasting of fuel.
In a high pressure engine, where the combustion chamber is designed for high pressure, high temperature combustion, injection systems must be designed to inject fuel at peak pressures at 200 to 400 atmospheres. The fuel must be injected in an appropriate manner to ensure that the actual fuel delivery coincides with the intended fuel profile. This is particularly important in electronic fuel delivery systems where the operating conditions are monitored electronically and fuel is metered according to engine performance and demand under control of a preprogrammed computer control system.
In multiple cylinder engines or in engines having one or more cylinders with multiple fuel injectors, it is customary to include a rail supply, which is essentially a high pressure fuel injector manifold, situated between the high pressure fuel injector pump and the fuel injectors. The rail supply holds a volume of high pressure fuel and operates as a surge control for modulating or buffering the periodic pulsing of the injectors. However, the high frequency pulsing of fuel released into the cylinders results in reflected pressure waves in the rail supply and other hydraulic components that appears to inhibit the fuel injector needle valve from seating and thereby fully closing the discharge orifices of the injector nozzle. In such a situation the actual fuel pulse has a long tail or injection dribble which is untimely to the operating cycle of the engine. Injection tail or leak results in incomplete complete combustion and pollution in the form of sooty or high carbon smoke.
The improved high pressure fuel injector of this invention eliminates post injection leak and cuts the trailing tail of the injection cycle at the point desired. The improved design enables substantial control over the injection cycle and renders the design of the fuel injector to be particularly applicable to electronically controlled fuel systems where the timing of the injector pulse can be varied electronically according to a predetermined system program.